This case study tells the story of a 30-year-old man with intractable peptic ulcer disease. The persistence of the ailment, despite medical treatment, prompts his healthcare provider to evaluate him for Zollinger-Ellison syndrome, a rare disease characterized by excess production of gastrin. Gastrin, a gastrointestinal hormone, promotes acid secretion in the stomach. The excess gastrin in Zollinger-Ellison syndrome often leads to gastrointestinal ulcers. In this case study, students work in small groups to review the physiology of gastrin and its role in digestion. The students then must assess the effect of excess gastrin levels on homeostasis, on the anatomy of the stomach and on the function of another gastrointestinal hormone, secretin. The case is designed for undergraduate students in an anatomy and physiology course or a pathophysiology course.